Wireless networks continue to evolve as new communication technologies develop and standardize. Wireless network operators can deploy new communication technologies in parallel with earlier generation communication technologies, and wireless networks can support multiple communication technologies simultaneously to provide smooth transitions through multiple generations of mobile wireless devices. Mobile wireless devices can include hardware and software to support wireless connections to different types of wireless networks that use different wireless communication technologies. Wireless networks using different radio access technologies (RATs) can overlap in geographic area coverage, and mobile wireless devices can support connections using different RATs depending on services and/or coverage available. A wireless service provider can provide services to mobile wireless devices through overlapping wireless networks, and mobile wireless devices can connect to one or more of the overlapping wireless networks. In a representative embodiment, a wireless service provider and/or a mobile wireless device can include simultaneous support for a Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) wireless communication protocol and a “legacy” third generation (and/or earlier generation) wireless communication protocol. Representative “legacy” protocols include the Third Generation Partnership Project 2 (3GPP2) Code Division Multiple Access (CDMA) 2000 1× (also referred to as 1×RTT or 1×) wireless communication protocol, the 3GPP Universal Mobile Telecommunications System (UMTS) wireless communication protocol, and the 3GPP Global System for Mobile Communications (GSM) wireless communication protocol.
Mobile wireless devices can include a combination of hardware and software to connect to multiple wireless networks that use different wireless communication protocols. Representative mobile wireless devices can support circuit switched (CS) voice connections through a first wireless access network that uses a legacy wireless communications protocol, e.g., the CDMA 2000 1× wireless communication protocol, and packet switched (PS) connections (voice or data) through a second wireless access network that uses the LTE wireless communication protocol. Additional representative mobile wireless devices can support CS voice connections through a UMTS wireless network or through a GSM wireless network and can support PS data or voice connections through an LTE wireless network. In some embodiments, the LTE wireless network and/or the mobile wireless device can be unable to support PS voice connections (yet able to support PS data connections), and the mobile wireless device can use a CSFB procedure to revert to a CS voice connection through a legacy wireless network. The mobile wireless device can operate in cooperation with the LTE wireless network and with the legacy wireless network to suspend a PS data connection with or disconnect from the LTE wireless network to originate or terminate a CS voice connection through the legacy wireless network, e.g., through a CDMA 2000 1× wireless network, a UMTS wireless network, or a GSM wireless network. While the mobile wireless device can use the LTE wireless network for PS data connections, when the mobile wireless device originates an outgoing voice connection or responds to an incoming voice connection, the mobile wireless device can transition from using the LTE wireless network to using a legacy wireless network that supports CS voice connections. When the CS voice connection completes, the mobile wireless device can subsequently return to the LTE wireless network for PS data connections.
The 3GPP standardized LTE wireless communication protocol specifies multiple options for CSFB procedures including messages and responses for when a mobile wireless device is in different connection states with the LTE wireless network. The LTE wireless communication protocol includes two possible connection states that can exist between the mobile wireless device and the LTE wireless network, namely a radio resource control (RRC) connected state and an RRC idle state. The CSFB procedures for each connection state can differ in the sequence of messages and responses communicated between the mobile wireless device and the LTE wireless network. In certain circumstances, the mobile wireless device and the LTE wireless network can become misaligned with respect to each other concerning the connection state that exists between them, e.g., the mobile wireless device can assume an RRC connected state exists with the LTE wireless network, while the LTE wireless network can assume an RRC idle state exists with the mobile wireless device. Following the standardized CSFB procedures, the LTE wireless network can send one or more messages to the mobile wireless device based on a first connection state, and the mobile wireless device can ignore the one or more messages from the LTE wireless network because it assumes a second different connection state. In such a scenario, the mobile wireless device can miss an incoming voice connection indicated by the LTE wireless network because of the misaligned connection states between the mobile wireless device and the LTE wireless network. Thus, there exists a need for a method to support alternate CSFB procedures to establish mobile terminated voice connections when the mobile wireless device is in one connection state, e.g., an RRC connected state, and the LTE wireless network assumes a different connection state, e.g., an RRC idle state.
The teachings described herein can be applied to mobile wireless devices that can operate in dual (or more generally multiple) wireless communication technology networks. In particular, the teachings disclosed herein can pertain to mobile wireless devices that switch from using one wireless technology for a first connection (e.g., a PS data connection) to another wireless technology for a second connection (e.g., a CS voice connection).